A-LevelBiologyHomeostasis9700/42 · May/June 2024 · Q108 Marks

In mammals, blood glucose concentration is maintained around a set point so that the mammal can function efficiently. This is an example of homeostasis.

(a)Name the mechanism that maintains blood glucose concentration around a set point.[1]
(b)Fig. 10.1 shows how the blood glucose concentration varies before, during and after a period of exercise. [Figure 10.1] Explain the results shown in Fig. 10.1 between 15 minutes and 70 minutes.[3]
(c)Type 1 diabetes in humans is a condition where the pancreas does not produce enough insulin to control blood glucose concentration. Test strips are used to measure the concentration of glucose in a sample of urine. Two reactions take place on the test strip and a colour change occurs if glucose is present in the urine. The equations for these reactions are: glucose + oxygen --(glucose oxidase)--> A + hydrogen peroxide hydrogen peroxide + B --(peroxidase)--> oxidised B + water
(c)(i)Identify compound A and the type of substrate represented by B. A B[2]
(c)(ii)Most people with diabetes mellitus use a biosensor to obtain their blood glucose concentration. Suggest the advantages of using a biosensor rather than test strips.[2]

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Mark scheme

Marking points from the official mark scheme (May/June 2024). The mark or mark type is shown in brackets.

[1] (a) negative feedback ;
[3] (b) any three from:
[3] (b) 1 (blood) glucose concentration decreases due to increased respiration or (blood) glucose concentration decreases due to glucose used to generate ATP for, muscle contraction / movement / exercise ;
[3] (b) 2 glucagon released (from pancreas) ;
[3] (b) 3 glucagon acts on liver cells ;
[3] (b) 4 glycogenolysis occurs / description ;
[3] (b) 5 glucose released into blood so (blood) glucose concentration, increases / returns to set point ;
[3] (b) 6 AVP; e.g. gluconeogenesis / ref. cell signalling
[2] (c)(i) A - gluconic acid / gluconolactone ;
[2] (c)(i) B - chromogen ;
[2] (c)(ii) any two from:
[2] (c)(ii) 1 measures, current / direct, blood glucose concentration ;
[2] (c)(ii) 2 accurate reading / quantitative / numerical / digital ;
[2] (c)(ii) 3 reusable ;
[2] (c)(ii) 4 AVP; e.g. can use regularly / convenient digital store of data / connected to phone or surgery

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